For a unfinished game there are sure shitload of people who love to play that game.
Most devs probably wish they sold as much as ARK, to be honest. ARK had a player estimate of 9,103,947 from the Steam player count leak in July (22nd from the top), comparatively, Fallout 4 had 6,601,188. And these numbers were supposed to be "low" and not accurate compared to the actual numbers. Keeping in mind this doesn't include the console totals.
If this has the same server setup as ARK (i.e. you can modify it for solo /co-op play to be like Terraria/Minecraft) it'll be pretty neat as that's the way I prefer to play these kind of games, and I know I'm in the minority on that one. Probably like ARK it will be best to wait until things get smoothed out but ARK came a LONG way from the initial Steam release. The last expansion for the season pass, Extinction, comes out this November.
It'll likely be on Xbox Game Preview as well, and have HDR.
I was wondering what Wildcard would make next, so I'll be looking into this. A lot of devs have joined them from major companies since they got bigger.